The present invention relates to cleaning apparatus in general, and more particularly to improvements in vacuum cleaners. Still more particularly, the invention relates to vacuum cleaners of the type wherein a liquid component (preferably a liquid component which contains a detergent and/or a disinfectant) is applied to the surface to be cleaned and is thereupon collected together with solid impurities and air.
German Pat. No. 569,799 discloses an electrical cleaning and sweeping apparatus wherein a vessel is subdivided into two chambers one of which contains a supply of clean liquid and the other of which serves for collection and storage of contaminated liquid. Clean liquid is drawn from the one chamber by a bladed impeller which cooperates with suitable ejector means and feeds a stream of clean liquid to a riser pipe which applies the liquid to the surface to be cleaned (e.g., to the floor). The thus applied liquid is thereupon collected from the surface by suction and is fed into the other chamber of the vessel. The collected liquid contains dust and air, i.e., it is a mixture of solid, liquid and gaseous components. Such apparatus are satisfactory for the cleaning of relatively small areas when a small supply of clean liquid suffices for the application to the surface to be cleaned, namely when the vessel can comprise a relatively small chamber for clean liquid and a relatively small chamber for contaminated liquid. However, the just described apparatus are not suited for largescale cleaning, e.g., of railroad cars, buses and similar vehicles for mass transport of persons. In many instances, the main supply of clean liquid is remote from the locus of use of the cleaning apparatus so that, in order to be capable of treating a large area (e.g., the interior or exterior of an entire coach), the apparatus must carry along large quantities of liquid which contributes to its bulk and energy requirements and limits its utility. Also, the contaminated liquid cannot always be disposed of in immediate vicinity of or close proximity to the surface or surfaces to be cleaned which means that a cleaning apparatus with a large supply of clean liquid must be transported a considerable distance from the main source of supply to the locale of use and a large supply of contaminated liquid must be transported from the locale of use to a disposal area.